Devices or machines for drilling a bore hole are known from the state of the art. The hammer tools are directly connected, several at a time, with the tool head here, so that the impact energy is transferred through the driving medium to the hammers plunged down into the bore hole. And from these directly to the bore hole floor, so that the connecting rod assembly remains uninfluenced by this to a great extent. The tool head is connected through the connecting rod assembly with a drive mechanism located outside of the bore hole, like a rotary drive unit, so that the hammers situated on the tool head work on areas of the bore hole floor that are always new. Work is primarily done with the devices at issue in solid rock.
This type of drilling has increasing significance in practice because, on one hand, the quality of the bore holes is better and the direction of the bore holes can be held on course nearly exactly; on the other hand, environmental criteria such as noise pollution are kept in significantly better compliance on the grounds of the sound-absorbing operating mode in the bore hole without any significant outside effect.
The removal of the rock material that has been hammered loose or scraped off from out of the bore hole can be done, in the case of systems of this type, within the hollow connecting rod assembly according to the so-called airlift process (reverse circulation). There is, in so doing, a fluid column in the bore hole, and air is blown into the drill column above the tool head like a scavenging fluid, so that a difference in pressure arises between the bore hole and the surface in the fluid column in the connecting rod assembly because of the air ascending in the connecting rod assembly. This difference in pressure induces in the connecting rod assembly a flow velocity with which the rock material is discharged through the connecting rod assembly.
When creating a hole in the ground via hammering, the inner diameter of the connecting rod assembly, which is available for the removal of the loosened material, has to have a certain minimum size that is adjusted to the total amount to be conveyed up. The rock chunks that are pounded loose also have larger dimensions in comparison to pure rotary drilling.
The fluid driving medium for the drilling hammers seated at the lower end of the connecting rod assembly is fed to the drilling hammers by the corresponding rotary connecting head at the upper end of the connecting rod assembly through a feeder constructed in or on the connecting rod assembly.
Problems result with regard to the seals of the rotary connecting head in the case of the relatively large diameters of the connecting rod assembly that are necessary, as mentioned.
Hammers that are driven hydraulically or pneumatically are operated at pressures of around 50 to 150 bar. It turned out that economical tool-life could not be achieved for the single seals previously used at the critical point of the transition between the fixed rotary connecting head and the rotating connecting rod assembly at these high pressures and with the airlift process requiring large diameters.
The problem involved with the invention is to improve a generic type of device in such a way that the device can be operated with longer repair-free periods with the larger external diameters of the hollow connecting rod assembly and the higher pressures that are necessary.